The collection of body fluids for diagnostic analysis has long been used in medical, diagnostic, forensic, veterinary medical and other fields to test and monitor for the presence of specific molecules within the fluid. Results of such analyte testing can be used to diagnose medical conditions, and to measure the concentration of pharmaceutical and other drugs or toxic substances in a human or animal subject. Analyte test results can also be used to monitor appropriate levels of therapeutic agents, or for other purposes. A subject's oral fluids may be used to test for a wide variety of types of molecules whose concentration in saliva is related to the circulating concentration of those molecules or related metabolites of substances in the blood. (Malamud, D, Saliva as a diagnostic fluid, Br. Med. J., 305, 207-208 (1990); Mandel, I. D, The diagnostic uses of saliva, J. Oral Pathol. Med., 19, 119-125 (1990); Mandel, I. D., Salivary Diagnosis: Promises, Promises, Malamud, D. and Tabak, L. (eds.); Saliva as a Diagnostic Fluid, Vol. 694: Annals of the New York Academy of Sciences, New York: The New York Academy of Sciences (1993), pp.1-8).
Use of saliva as a medium for analysis is desirable since it can be obtained by noninvasive methods, unlike blood product collection methods that involve trained medical personnel and use venipuncture or finger-stick methods of collection. Oral fluid collection can also be done in public without requiring privacy booths, bathroom facilities, and careful subject monitoring otherwise required to avoid adulteration, sample replacement, sample dilution and other problems associated with urine collection. A number of sample collection assemblies and methods have been disclosed. For example, U.S. Pat. No. 6,022,326 issued to Tatum et al., which is fully and expressly incorporated herein by reference, describes a device and method for automatically collecting saliva from a subject through aspiration using a wand with an associated saliva collection tip and a vacuum that flows the saliva from the tip, through the wand, and into a collection chamber. After the saliva sample is collected, it is typically sent to a specialized laboratory for analysis.
Many different assay methods for measuring an analyte in a sample are known in the art. Many of such methods are immunological based, i.e., they involve measuring the binding of an antibody or antibody fragment to a complementary ligand, e.g., a drug or other molecule. Immunoassay methods, in general, are based on the competition between a specific analyte, the concentration of which is to be measured in a sample, and a known amount of tracer, which is generally the analyte or an appropriate analog antigen thereof in labeled form, with the analyte and tracer competing for a limiting number of available binding sites on a binder. U.S. Pat. Nos. 5,183,740 and 5,354,654 issued to Ligler et al., which are hereby fully and expressly incorporated herein by reference, disclose these immunoassay methods in further detail.
Typically, semi-automated or automated systems are used to load and perform immunoassay tests on the saliva samples. The majority of the systems on the market comprise a loading tray for loading multiple samples, which are not necessarily of the same nature or having the same assay performed on them. There is also a reagent tray that holds a number of reagent cartridges for the various different tests to be performed. In the machine, the samples are transferred, normally by pipetting into an assay cell, where the sample is combined with the necessary reagent or reagents. The assay cell is then transferred to a part of a machine where it can be held for sufficient time for the reagent and the sample to combine. Thereafter, the sample cell is transferred to the detector, which detects the presence of a known indicator to determine whether or not the sample contained a particular component and/or how much of that component was present in the assay.
Recent systems have employed flow injection technology, which involves combining the sample in a fluid stream that passes through a reaction column containing a support medium on which antibodies are bound and saturated with a labeled antigen. The fluid stream passes over the support media, where competition between any analytes and the labeled antigen occur. Any displaced labeled antigen passes out through the reaction chamber and into a transparent detection chamber where it is detected and quantified, e.g., by fluorescent means, as an indication of the presence and quantity of the specific analyte to be tested. U.S. Pat. Nos. 5,370,842, 5,779,978, 6,120,734, 6,159,426, as well as previously mentioned U.S. Pat. No. 5,183,740, discuss this flow injection technology in some detail.
The above-described methodologies are sufficient for some applications, e.g., those applications in which time is not critical. For other applications that require portability and/or real-time testing of the sample, e.g., in police stations, emergency rooms, etc., sending a sample to a laboratory for analysis is simply not practical. In response to the need to decrease the amount of time required to obtain test results from a sample, as well as the need to provide more convenient and less expensive diagnostic methods, there have been efforts to develop simple tests to allow unskilled persons to perform certain analytical procedures outside of the laboratory. For example, U.S. Pat. No. 5,145,789 describes a method for testing urine. As previously mentioned, however, there are various problems that are associated with urine collection and testing.
Other methods, such as those described in U.S. Pat. No. 4,703,017, 5,556,789, and 5,714,341, require a two-step process, which involves collecting the specimen, and then manually applying the collected specimen to the analytical device. Thus, at least two operations and devices are necessary with these previous methods. First, collection of the saliva specimen with some type of collection device and, second, application of the saliva specimen to the analytical device described in those inventions. Thus, these methods are disadvantageous in that they are not performed in real time and requires additional handling by users, posing a risk that errors may be unknowingly introduced into the test results.
U.S. Pat. No. 6,248,598 describes a method that collects the saliva and initiates an assay or assays of the saliva in one step. This method, however, requires the use of a saliva absorption technique, which has significant limitations, including slow collection times, risk of irreversible absorption into the carrier membrane, inability to obtain quantitative results, and a limitation of the number of different tests that can be performed on the small sample size.
There thus remains a need for improved systems, methods, and assemblies that test or facilitate in testing bodily fluids for target analytes, e.g., drugs in saliva.